1. Field of the Invention
This invention relates generally to improvements in cleaning apparatus of the type used, for example, in electrostatic document printers or copiers to remove residual toner, carrier, dust, lint, paper fibers and the like from a moving surface, typically in the form of an endless web or drum.
2. Discussion of the Prior Art
Heretofore, blade cleaners have been used in electrophotographic copiers and printers to remove particulate material, e.g., toner, carrier, dust, lint, paper fibers, and the like, from various moving surfaces within the instrument. Such surfaces typically include the relatively delicate outer surfaces of image-recording and image-transfer elements, as well as the somewhat less delicate surfaces of endless webs used to transport a sheet material from one image processing station to another.
Blade cleaners are often classified by the way they operate to clean the moving surface they contact. Some operate in a xe2x80x9cscrapingxe2x80x9d mode; others operate in a xe2x80x9cwipingxe2x80x9d mode. When operating in a scraping mode, the blade element is set at an obtuse angle (typically between 100 and 120 degrees) relative to the oncoming surface it is intended to clean. Thus, the blade edge opposes the movement of the surface and deflects particulate material from the surface as it initially engages the blade edge. When operating in a wiping mode, the blade element is set at an acute angle (typically between 60 and 85 degrees) relative to the oncoming surface it is to clean. Thus, the blade edge extends slightly in the direction of travel of the moving surface, and particles are wiped from the surface as the surface moves away from the blade edge. Obviously, the scraping mode is harsher on the moving surface and usually requires a lubricant to prevent the blade from becoming unstable and tucking under. In applications where considerable amounts of toner (which serves as a blade lubricant) remain on a surface for cleaning, scraping blades are often preferred, since they are more flexible to machine configuration. In applications that require long runs without toner or any other self-lubricating material, wiper blades are preferred due to their inherent stability. Both types of blade cleaners (i.e., scrapers and wipers) are disclosed in U.S. Pat. No. 5,426,485 in which cleaning blades serve to remove particulate material from an endless elastic belt used to convey copy sheets in an electrostatic copier. In this patent the pressure applied by the blade is adjustable as a function of belt temperature.
U.S. Pat. No. 4,866,483 discloses a blade-type cleaning station for a table-top electrostatic printer. A pair of spaced, parallel cleaning blades, set to operate in a wiping mode, serve to remove residual toner from an endless photoconductive image-recording belt following transfer of a toner image to a copy sheet. The cleaning station further includes a rotatably driven auger for transporting most of the scavenged residual toner collected in a sump to a remote receptacle for removal. The cleaning station is stationary within a printer""s base frame, and the entire print engine, including the image-recording belt, is mounted on a pivoting frame for movement between closed and open positions, toward and away from the cleaning station. In its closed position, the print engine""s image-recording belt pressingly engages the respective edges of the cleaning blades and is thereby positioned to be cleaned by the blades as the belt advances along its endless path. In its open position, the belt is sufficiently spaced from the blades so that the cleaning station may be readily serviced, e.g., to vacuum scavenged toner from that portion of the sump directly beneath the cleaning blades, or to replace the cleaning blades themselves. Here, the blades are loosely supported at opposite ends in a pair of guide channels formed in the end walls of the sump housing. Each blade has a pair of downwardly depending pegs at opposite ends. These pegs fit into the central portion of a coil spring located in each guide channel, such coil springs acting to urge the blades into contact with the moving belt when the print engine frame has been returned to its closed position. In use, the cleaning blades operate on an unsupported region of the image-recording belt.
While the cleaning station disclosed in the above-noted patent affords certain advantages not found in prior devices, it may still be viewed as problematic in certain respects. For example, the sump housing that receives toner wiped from the belt surface by the blade cleaners is relatively small, thereby requiring the relatively costly auger system to continuously transport particles to a remote location for storage prior to removal. Further, while ready access may be gained to the cleaning station by simply pivoting the print engine frame to its open position, there is no fool-proof way of removing the scavenged particulate material from the blade housing (sump) without some potential for blowing the particles throughout the machine frame. Once the print engine has been pivoted to its open position to gain access to the scavenged particle sump for vacuuming, the entire sump is exposed to ambient air, and any air currents in the vicinity of the open sump can have the effect of blowing toner, throughout the instrument. Ideally, the scavenged particle sump should be easily removed from the vicinity of the machine frame while scavenged particles are confined therein. Once removed, the sump may be discarded and replaced with a new sump, or it may be cleaned at a location safely spaced from the machine and then replaced. Also, since there is no lid or cover on the top of the sump, scavenged particles can escape the sump and contaminate the machine elements while the machine is in operation. Further, since there is no hard back-up for the web to resist the pressure applied on the web by the cleaning blades, the web is likely to stretch over time, thereby changing the dynamics at the blade edge/web interface.
In view of the foregoing, an object of this invention is to provide a blade-type cleaning apparatus of the above type that overcomes the noted disadvantages of the prior art devices.
Another object of this invention is to provide a relatively low-cost, operator-replaceable cartridge comprising one or more wiper blades supported by an enclosed particle sump that is easily removed from a printer/copier so that the cartridge may be serviced away from the machine or, alternatively, discarded and replaced with a new cartridge.
A further object of this invention is to provide an improved method for cleaning particulate material from a moving surface.
As will become more apparent from the ensuing detailed description of preferred embodiments, these and other objects of the invention are realized, in accordance with a first aspect of the invention, by the provision of a web-cleaning apparatus comprising an operator-replaceable cleaning cartridge adapted to be releasably supported by a bracket in a position to engage a moving surface of a web to be cleaned. Such cleaning cartridge comprises (a) a pair of cleaning blades each comprising an elongated rigid member with a flexible blade member; (b) a sump housing for releasably supporting the blades in a spaced parallel relationship and for receiving and storing particulate material removed from the moving surface by the blades; and (c) a lid assembly, operatively connected to said sump housing to form a substantially enclosed chamber therewith. The sump housing has a pair of opposing end walls, each defining a pair of spaced notches for receiving and supporting an end of one of the blades. The notches are positioned to locate the respective edges of the blades in a spaced, parallel relationship, with each of the flexible blade members extending at a predetermined acute angle relative to a planar upper surface of the lid assembly. The lid assembly comprises a lid member defining an elongated opening through which the flexible blade members of the wiper blades project when the wiper blades are supported in the notches of the sump housing. The opening in the lid has a rectilinear lip supporting a flexible seal blade having a rectilinear edge spaced from said wiper blades and extending parallel thereto. The seal blade is substantially more flexible than the flexible blades of the wiper blades and, in addition to sealing the upstream end of the sump housing to prevent the escape of scavenged particles, also operates to deflect into said enclosed chamber particulate material wiped from a moving surface by at least one of the wiper blades. Preferably, the lid member defines an open auxiliary reservoir for receiving any particulate material wiped from the moving surface by the seal blade. Also preferred is that the upper surface of the lid member supports at spaced, parallel locations, two strips of a compressible material which cooperate with the moving surface to prevent particulate material in said sump from escaping from the sides of the sump housing. The cartridge is easily accessible to the operator by means of a bracket, described in the above-referenced U.S. patent application, filed concurrently herewith, that is releasably latched to a hard backup assembly and can be quickly unlatched and dropped for easy installation, service and removal of the cleaning cartridge. The cartridge-supporting bracket can also be quickly removed from the backup assembly for installation or removal of a transport or transfer web.
In accordance with another aspect of the invention, the web-cleaning apparatus of the invention comprises, in addition to the above-noted cleaning cartridge, a hard back-up member or xe2x80x9cshoexe2x80x9d that is positioned on the opposite side of the moving web from the wiper blades of the cleaning cartridge. Preferably, the back-up member is part of a two-piece bracket assembly used to releasably support and position the cleaning cartridge relative to the web surface and a backup shoe or pressure plate in order to achieve a uniform pressure across the web.
Due to the construction of the operator-replaceable cleaning cartridge, a machine operator can perform periodic maintenance on the cleaning station with minimum downtime. Moreover, the application of the cleaning blades against a stationary hard backup minimizes any adverse effect the blades might have on the web-tracking system and on color registration (e.g., in a full color document printer) since the stationary backup does not steer the web, and the blades are designed with enough compliance to reduce load variations due to differential in engagement between front and rear of the cleaner, as may be found in other applications where the blades abut against a roller, and the blades are considerably stiffer. Also advantageous is that an auxiliary waste reservoir in the lid assembly serves to contain any particles that may get deflected in a direction upstream of the cleaning blades. While the first blade that contacts the web does the bulk of the cleaning work including the function of trapping paper dust, fibers, lint and oil from the transport web, the second blade then continues the cleaning process, thereby extending the cleaning function of the cleaning station over longer periods of time. The dual wiper blades ensure consistency and extended life cleaning performance while avoiding the problems of instability or tuck-under encountered with scraper blades. The efficiency of the first blade in trapping fibers, lint and other debris eliminates the need for a fur brush.
The invention and its various advantages will be better understood from the ensuing detailed description of preferred embodiments, reference being made to the accompanying drawings in which like reference characters denote like parts.